(1) Field of the Invention
The present invention relates to a mobile machine for correcting the position of a track and for tamping the track, which comprises an elongated machine frame mounted on the track for moving in an operating direction and a ballast tamping assembly mounted on the machine frame and including tamping tools arranged to tamp ballast under respective track ties. A track lifting and lining unit for correcting the position of the track is mounted on the machine frame adjacent the ballast tamping assembly and preceding the ballast tamping assembly in the operating direction, and the track lifting and lining unit comprises a tool carrier frame extending in the direction of elongation of the machine frame, two pairs of flanged wheels supporting the tool carrier frame on the track rails, and at least two track lifting tools arranged on the tool carrier frame for adjustable engagement with each rail. Lifting and lining drives have respective ends linked to the tool carrier frame and to the machine frame.
(2) Description of the Prior Art
U.S. Pat. No. 4,323,013, dated Apr. 6, 1982, discloses a compact track leveling, lining and tamping machine comprising an elongated machine frame supported on the track by two widely spaced undercarriages, a ballast tamping assembly and a track lifting and lining unit mounted on the machine frame between the undercarriages, which comprises a rigid tool carrier frame whose rear part adjacent the ballast tamping unit is linked to the machine frame by lifting and lining drives which are operatively controlled by a track leveling and lining system, and whose front part is a pole projecting forwardly from the rear part and is linked to the machine frame. A pair of flanged wheels supports the tool carrier frame on the track rails and the flanged wheels serve as track lining tools transmitting the lining forces to the rails. The track lifting tools are mounted on each longitudinally extending side of the tool carrier frame and comprise, per rail, two pairs of tong-like lifting rollers spaced from each other in the direction of elongation of the machine frame and a lifting hook arranged therebetween, with respective drives for vertically and laterally adjusting the lifting hook. The lifting rollers are transversely pivotal by independently operable drives for tong-like engagement with the respective rail. Such a track lifting and lining unit is capable of sustaining considerable lifting and lining forces, which makes it very useful for operation in track switches, which are very heavy. In such operations, the lifting hooks are of great advantage since they may be vertically adjusted for gripping either the rail foot or head, depending on whether they are used in a crib area or at a tie. Alternatively or in addition, depending on the configuration of the track section, the lifting rollers may be selectively engaged with the associated rail. The arrangement may also be used in tangent track sections, preferably by engaging both pairs of flanged lifting rollers with the track rails for so-called two-point lifting. At the points of abutment of two rail ends, one of the pairs of flanged wheels may be readily pivoted out of engagement with the rails at these points where the pair of flanged wheels remaining in engagement with the rails serves for a brief period of time to lift the track.
U.S. Pat. No. 3,799,058, dated Mar. 26, 1974, also discloses a mobile track leveling, lining and tamping machine with a two-point track lifting arrangement, the track lining tools comprising two pairs of flanged wheels supporting the tool carrier frame of a track lifting and lining unit on the track rails. The two pairs of flanged wheels are spaced from each other in the direction of elongation of the machine frame and are arranged between two pairs of tong-like track lifting rollers. The lifting and lining tools for each rail are mounted on a respective tool carrier frame whose front end is vertically adjustably linked to the machine frame in a vertical guide column and is connected to a hydraulic lifting and lining drive. This two-point lifting and lining enables tangent track to be repositioned efficiently since the lifting and lining forces can be advantageously distributed to two spaced rail points without subjecting the rail fastening elements to undue stress, such track leveling or lining also preventing undue bending or flexing of the rails.
U.S. Pat. No. 3,832,952, dated Sept. 3, 1974, describes a mobile track leveling, lining and tamping machine wherein the track lifting and lining tools are mounted on a transversely extending support beam linked to the machine frame by lifting and lining drives arranged in a vertical plane and by longitudinal adjustment drives arranged in a horizontal plane and linking the ends of the support beam to the machine frame. A flanged roller of very small diameter supports the support beam on each rail and serves as lining tool. A respective vertically and transversely adjustable lifting hook is mounted on the support beam opposite each flanged lining roller but staggered from its axis in the direction of elongation of the machine frame. To enable the lifting hook to engage the associate rail at a fish plate or a like obstacle, the support beam may be pivoted about a central vertical axis by a respective longitudinal adjustment drive, which disadvantageously affects the transmission of the lining forces in a direction extending obliquely to the track. The relatively light construction of the track lifting and lining unit incorporating small lining rollers and a single lifting tool per rail makes it impossible to use such a machine effectively in heavy switches or other complex track sections.